Refractory-coated oxygen lance



7 Nov. 14, 1967 E. w. KOENIG ETAL 3,352,552 REFRACTORY-COATED OXYGENLANCE,

Filed July 8, 1965 //VV/V7'0/P5. E. WALTER KOENIG GERALD R. COPE UnitedStates Patent Ofi 3,352,552. Patented Nov. 14, 1967 ice 3,352,552REFRACTORY-COATED OXYGEN LANCE Edward Walter Koenig, Denver, Colo., andGerald R.

Cope, Johnstown, Pa., assignors to Harhison-Walker Refractories Company,Pittsburgh, Pa., a corporation of Pennsylvania Filed July 8, 1965, Ser.No. 470,547 2 Claims. (Cl. 266-34) ABSTRACT OF THE DISCLOSURE An oxygenlance construction of the type particularly suited for use in anelectric furnace comprised of an elongate, open-ended, tubular metalmember having firmly anchored about a substantial portion of itsexterior surface a hard refractory sheath, said sheath fabricated from apaste-like mixture of phosphoric acid and material of the group highalumina materials, and zircon.

This invention relates to improved oxygen lance construction. Moreparticularly, the invention relates to oxygen lances of the type usefulin the manufacture of steel by contemporary ogygen processes; forexample, introduction of oxygen or air into electric furnaces or thelike to assist in more rapid removal of carbon and like impurities toobtain high quality steel.

In the manufacture of steel by various oxygen-utilizing processes, it isconventional to use an elongate, tubular member to rapidly blow oxygenover the surface of a molten metal bath. As one can imagine, the veryhigh temperatures of the environment in such a steelmaking vessel isextremely destructive to the tubular members or lances.

It has been suggested that water jackets be utilized about exteriorsurfaces of the oxygen confining tube, but this would not besatisfactoryparticularly adjacent the lower ends of the lance which are,in fact, destroyed and worn away in use-since it would allow escape ofwater, or such other cooling fluid as might be used, into the moltensteel. In fact, it seems as though almost any approach to solving theproblem of increased oxygen lance life is one which merely slows downthe rate of destruction of the lance. It has been suggested that variousrefractory materials could be placed over exterior surfaces of the lanceto thereby slow down its destruction. One suggestion has been to coat asheet of paper with a refractory and to then roll this refractory-coatedpaper about the tube. Of course, the paper is destroyed almostimmediately when exposed to the atmosphere of a steelmaking furnace,thereby providing a plane of weakness through the coating which promotesspalling or peeling off of large chunks of the refractory.

Therefore, it is an object of this invention to provide a new lanceconstruction particularly suited for use in certain metallurgicalprocesses utilizing oxygen, which lance construction markedly retardsthe rate of destruction of the lance over those portions exposed tosteelmaking furnace environments.

Briefly, according to a preferred embodiment of this invention, anoxygen lance construction is provided which is comprised of an elongatemetal, preferably steel, pipe or tube, over the exterior surfaces ofwhich is firmly bonded a particular refractory composition. In the mostpreferred construction, the refractory is applied as a series of layers,which layers firmly bond to each other, and whichafter a bakingtreatment-form a substantially monolithic refractory sheath aboutexterior surfaces of the oxygen-confining tube or pipe.

The preferred refractory composition is a paste-like compositionconsisting essentially of -25%, based on the weight of solids in thepaste, of wet 75% phosphoric acid (or equivalent wet acid providing thesame amount of P 0 with the remainder of the paste substantially allbeing a member selected from the group consisting of high aluminamaterials and zircon. The selected high alumina material and the zirconare substantially free of materials which will vitrify or form glassyphases at temperatures of about 2000 F.

High alumina materials has a well understood meaning in the art. Highalumina materials are generally classified by their A1 0 content intogroups having approximately 50, 60, 70, 80, 90, or 99% A1 0 by oxideanalysis. Such refractories can be made by blending various high aluminarefractory materials or by using selected ones having the desired A1 0content. The more common high alumina refractory materials and theirtypical A1 0 contents are: calcined Baer process alumina, 99% A1 0calcined South American bauxite, having 88% A1 0 calcined Alabamabauxite, having 74% A1 0 calcined diaspore, having 76% A1 0 burleydiaspore, having 48- 88% A1 0 kyanite, having 56% A1 0 etc. All of thesematerials are, of course, chemically compatible. Further, minoradjustments in A1 0 content are commonly accomplished by including smallamounts of clay or silica.

Zircon is generally represented by the formula A usable zircon materialof sand sizing has an oxide analysis substantially as follows: 66.1% ZrO 32.3% SiO 1% A1 0 and 0.2% each of TiO and Pe O Total alkali contentruns on the order of 0.2%.

The type of steel used for our lance construction is, of course,variable, depending upon the desires of the user or fabricator and basedon such considerations as price, temperature of use, etc. However, it isessential that the steel be of such a type as to react over its exteriorsurfaces with the phosphoric acid content of the refractory-phosphoricacid paste.

A preferred method of constructing the lances of this invention is asfollows: A length of selected steel pipe or tubing of desired inner andouter diameter is coated with a relatively thin layer of the Wet pastymixture, described above. After a substantially even coating has beenapplied, the construction is passed through an oven and subjected to atemperature on the order of about 450 F. for about 15-30 minutes, duringwhich time the acid reacts with the exterior surfaces of the pipe,roughening it, and promotes a firm bond between the paste coating andthe pipe, as well as curing the paste to a hard state. The heat-treatedmember is then recovered and an additional coat or coats of the paste isapplied with the heat treatment being repeated after each coating. Thesubsequent applications of wet paste-like material react with previouslyapplied and set coatings. The result is an oxygen lance constructionconsisting of a central, metal, tubular conduit open at each end, andabout exposed exterior surfaces of which there has been interaction withand firm bonding to a monolithic sheath of highly refractory material.

Just as the size of the tubular member is dependent upon use and thevarying requirements of the user, the thickness of individual coatingsand the total thickness of the final sheath is variable. However, in theinterests of a complete disclosure, a usable lance construction,according to the best mode now known for the practice of our invention,is comprised of an inner, black steel pipe having an inside diameter ofabout /2", and a wall thickness of about A". The total sheath thicknessis about one inch, being built up of multiple coatings.

The attached drawing schematically indicates a lance constructionaccording to this invention. In the drawing there is shown a lancecomprised of an elongate, hollow, metal, core member 10 about theexterior surface of which is a set or cured layer of refractory 11 whichis firmly bonded to exterior surfaces of the conduit 10 over all exposedsurfaces, i.e., completely over the core-refractory sheath interface 12.Preferably the ends 10A of the core member or pipe 10 are threaded forabout 1" to allow the stub end of a used lance to be attached to anew'lance and completely consumed.

Having thus described the invention in detail and with sufficientparticularity as to enable those skilled in the art to practice it, Whatis desired to have protected by Letters Patent is set forth in thefollowing claims.

We claim:

1. An oxygen lance construction comprised of an elongate, open-ended,tubular, metal member, the material of which said metal member isconstructed being capable of reacting with phosphoric acid, and a hardrefractory sheath firmly anchored to and surrounding all exteriorsurfaces of said metal member, said refractory sheath being made from apaste-like batch containing phosphoric acid in an amount sufficient toprovide the equivalent of 15- 25% of 75% phosphoric acid based on theweight of the solids in the paste, the solids consisting essentially ofrefractory material selected from the group consisting of high aluminamaterials and zircon.

2. An oxygen lance construction comprised of an elongate, open-ended,tubular, metal member, the material of which said metal member isconstructed being capable of reacting with phosphoric acid, and a hardrefractory sheath firmly bonded and anchored to and surrounding allexterior surfaces of said metal member, said refractory sheath beingmade from a paste-like batch containing phosphoric acid in an amountsufiicient to provide the equivalent of l525% of 75% phosphoric acidbased on the weight of the solids in the paste, said solids consistingessentially of refractory material selected from the group consisting ofhigh alumina materials and Zircon, said sheath comprised of a pluralityof monolithically bonded layers of said batch.

References Cited UNITED STATES PATENTS 2,790,740 4/ 1957 Ayres et al.1486.l5 3,045,997 7/1962 Hudson 26 634.l 3,121,038 2/1964 Perotte1486.15 X

J. SPENCER OVERHOLSER, Primary Examiner.

E. MAR, Assistant Examiner.

1. AN OXYGEN LANCE CONSTRUCTION COMPRISED OF AN ELONGATE, OPEN-ENDED,TUBULAR, METAL MEMBER, THE MATERIAL OF WHICH SAID METAL MEMBER ISCONSTRUCTED BEING CAPABLE OF REACTING WITH PHOSPHORIC ACID, AND A HARDREFRACTORY SHEATH FIRMLY ANCHORED TO AND SURROUNDING ALL EXTERIORSURFACES OF SAID METAL MEMBER, SAID REFRACTORY SHEATH BEING MADE FROM APASTE-LIKE BATCH CONTAINING PHOSPHORIC ACID IN AN AMOUNT SUFFICIENT TOPROVIDE THE EQUIVALENT OF 1525% OF 75% PHOSPHORIC ACID BASED ON THEWEIGHT OF THE SOLIDS IN THE PASTE, THE SOLIDS CONSISTING ESSENTIALLY OFREFRACTORY MATERIAL SELECTED FROM THE GROUP CONSISTING OF HIGH ALUMINAMATERIALS AND ZIRCON.